When taking a picture, it is necessary to know not only in what direction to aim the camera but also how much of the subject will be included in the picture. For this reason practically every camera has a viewfinder of some kind.
There are known cameras that are intended to take pictures having various formats. For example, the pictures may be interspersed full-size exposures about 36.6 mm.times.24.4 mm (length.times.height) and reduced-height panoramic exposures about 36.6 mm.times.13.3 mm. The viewfinder for these cameras has a masking device for changing the format, i.e. the aspect ratio, of the view through the viewfinder in accordance with the format of the exposure to be made. The 36.6 mm.times.24.4 mm exposure has an aspect ratio of 1.5:1, and the 36.6 mm.times.13.3 mm exposure has an aspect ratio of 2.75:1.